External cues (ex- growth factor) protein released by cells stimulates other cells to divide. Density dependent inhibition prevents crowded cells from dividing. Cultured cells divide to form single layer, then stop. Anchorage dependence allows many cells to be attatched to substrate to divide and may be effect of plasma membrane proteins.

Binary Fission in Prokaryotes

Cells divide without mitosis. Single bacterial chromosome replicates.

No miotic spindle formation which is how chromosomes separate is not clear. Plasma membrane pinches off cells and grows inward, new cell wall deposited.